The van der Waals interaction between colloidal particles and its molecular interpretation

We discuss the relation between a description of the van der Waals interaction between colloidal particles based on a molecular picture of matter with the Lifshitz description based on quantum electrodynamics. The main observations are as follows: (i) Starting from the Lifshitz description one can derive the exact Hamaker result for the dispersion interaction by applying the Clausius-Mossotti formula relating the dielectric permittivity of a medium to the polarizability of the molecular units. The Hamaker result appears as a leading term and the first correction term fully corresponds to the Axilrod-Teller three-body correction to the dispersion interaction. (ii) It is pointed out that the so called zero frequency term in the Lifshitz expression for the Hamaker constant has contributions from both quantum and classical molecular degrees of freedom and that the conventional interpretation of this term is quantitatively incorrect. (iii) An expression for the interaction between two classical dipolar media is derived using a recently published conjecture.